In the case of certain hydroformed parts, there is the requirement that one or more other components be detachably fastened thereto for the purpose of forming an assembly therewith. For example, certain hydroformed motor vehicle components such as a motor vehicle frame member. Wherein one or more other frame components are required to be firmly fastened thereto to form a frame assembly. In order to accomplish this, suitable fastening means are normally added to the hydroformed part in a secondary operation to provide for such attachment of these other components.
One well-known practice is to accomplish this by the attachment of a suitable fastener nut at the required location in a secondary operation following the removal of the hydroformed part from the hydroforming dies. Wherein a hole is formed in the part such as with a drilling, laser or water jet cutting operation at each attaching location and then locating and welding a weld-nut in place or locating and mechanically fastening a rivet-nut in place.
Another manner of obtaining a suitable means of attachment is known as hydrotapping and is disclosed in U.S. Ser. No. 10/690,100 filed Oct. 21, 2003 and entitled “Hydrotapping Unit” and assigned to the assignee of the present invention. Wherein the hydroformed part is pierced and there is then formed an inwardly projecting collar in the part, and the collar is then tapped to form an internal thread of substantial length. This is accomplished while the hydroformed part remains in the hydroforming dies and still under the hydroforming pressure that then supports the piercing and collar forming operations. As a result, this significantly reduces the time to process the part as compared with requiring a secondary operation following removal of the hydroformed part from the dies.